Electrical conduction and space charge formation in partially crystalline polymers

Polarization currents and thermally stimulated depolarization currents have been measured from semicrystalline polypropylene samples with varying manufacturing parameters influencing the structural properties. The effect of interfacial polarization on short-circuit TSD is theoretically explained by a simple three-layer model representing different structural regions of the polymer. It is shown that half width and height of the corresponding TSD-peak is affected by the structure. A method is presented to study the influence of ohmic conduction on TSD of two-sided metallized samples using an external capacitor. A negative space-charge in the cathode region is qualitatively revealed by scanning non-metallized fracture planes of PP with an electron microscope of low beam current and energy.